Stumped on what to call the baby? Some places give you more time to decide than others. EHStock/iStockphoto hide caption toggle caption EHStock/iStockphoto The Two-Way William And Kate Took 2 Days. How Long Can You Wait To Name A Baby? July 25, 2013 The Duke and Duchess of Cambridge broke with recent tradition with their quick announcement of Prince George's name. That got us wondering just how long parents have to name a new bundle of joy.